On Fri, Feb 03, 2017 at 02:32:37PM +0100, Takashi Iwai wrote:
> On Thu, 02 Feb 2017 11:12:53 +0100,
> Takashi Iwai wrote:
> >
> > The audio chicken bit (register offset 0x62f38) seems required to make
> > DP audio working on some machines. At least, on Dell Wyse 3040, I
> > failed to get the audio unless this bit is set once.
> >
> > Strangely, the bit seems necessary only once, and it persists after
> > that, even some power-off cycles. The register is supposedly
> > write-only, so it's no evidence whether the bit keeps effect
> > persistently. But, judging from the experiment, it looks enough to
> > set it up once at the device initialization.
> >
> > The patch is basically a cut from the original patch by Pierre-Louis
> > Bossart.
> >
> > Cc: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
>
> I gave a typo to intel-gfx ML address, now corrected, sorry.
>
> Are you i915 guys OK with this change? I'd love to fix it for 4.11 in
> time, so please check and give ACK.
>
>
> thanks,
>
> Takashi
>
> > ---
> > drivers/gpu/drm/i915/i915_reg.h | 3 +++
> > drivers/gpu/drm/i915/intel_lpe_audio.c | 7 +++++++
> > 2 files changed, 10 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index 4e24ba0cdbe8..4f15a3dc6d98 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -2062,6 +2062,9 @@ enum skl_disp_power_wells {
> > #define I915_HDMI_LPE_AUDIO_SIZE 0x1000
> >
> > /* DisplayPort Audio w/ LPE */
> > +#define VLV_AUD_CHICKEN_BIT_REG _MMIO(VLV_DISPLAY_BASE + 0x62F38)
> > +#define VLV_CHICKEN_BIT_DBG_ENABLE (1 << 0)
> > +
> > #define _VLV_AUD_PORT_EN_B_DBG (VLV_DISPLAY_BASE + 0x62F20)
> > #define _VLV_AUD_PORT_EN_C_DBG (VLV_DISPLAY_BASE + 0x62F30)
> > #define _VLV_AUD_PORT_EN_D_DBG (VLV_DISPLAY_BASE + 0x62F34)
> > diff --git a/drivers/gpu/drm/i915/intel_lpe_audio.c b/drivers/gpu/drm/i915/intel_lpe_audio.c
> > index d3ffe0012692..3ba2799e93bd 100644
> > --- a/drivers/gpu/drm/i915/intel_lpe_audio.c
> > +++ b/drivers/gpu/drm/i915/intel_lpe_audio.c
> > @@ -248,6 +248,13 @@ static int lpe_audio_setup(struct drm_i915_private *dev_priv)
> > goto err_free_irq;
> > }
> >
> > + /* enable chicken bit; at least this is required for Dell Wyse 3040
> > + * with DP outputs (but only sometimes by some reason!)
> > + */
> > + I915_WRITE(VLV_AUD_CHICKEN_BIT_REG,
> > + I915_READ(VLV_AUD_CHICKEN_BIT_REG) |
> > + VLV_CHICKEN_BIT_DBG_ENABLE);
RMW seems a little pointless since you verified that the register can't
actually be read.
So, with the read dropped
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > +
> > return 0;
> > err_free_irq:
> > irq_free_desc(dev_priv->lpe_audio.irq);
> > --
> > 2.11.0
> >
--
Ville Syrjälä
Intel OTC
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